C172 AND A PA44 HAD LESS THAN LEGAL SEPARATION WHEN PA44 LANDED ON OCCUPIED RWY.

Narrative

UPON LNDG ON RWY 9L AT SANFORD; THE AIRPLANE BEGAN VIBRATING. MY CFII STUDENT PERFORMED THE NORMAL LNDG AND TOUCHDOWN SEEMED SMOOTH; BUT SLOWED MORE RAPIDLY THAN NORMAL AND THE PLANE BEGAN TO SHAKE. I INITIALLY THOUGHT IT TO BE THE SHIMMY DAMPER; SO I PULLED BACK ON THE CTL YOKE. BEFORE WE KNEW IT THE AIRPLANE HAD STOPPED AND TWR IS TELLING US TO GET OFF THE RWY. LITTLE DO THEY REALIZE THAT WE HAVE A PROB AND ARE TRYING TO STEER THE PLANE OFF THE RWY AT TXWY R. LITTLE DID WE REALIZE THAT A SEMINOLE PA44 HAD ALREADY LANDED BEHIND US AND DID NOT SEE US STILL TRYING TO GET OFF THE RWY. UPON CLRING THE RWY WE RECEIVED PERMISSION TO SHUT DOWN AND CHK WHAT WE SUSPECTED TO BE A FLAT TIRE. ONCE OUT OF THE PLANE; I COULD CONFIRM THE L TIRE WAS FLAT. THIS WAS OUR FIRST AND ONLY LNDG ON THIS FLT AFTER SHOOTING MULTIPLE APCHS (1.7 HRS ON HOBBS). I DO NOT KNOW THE CAUSE OF THE FLAT TIRE. PREFLT INSPECTION REVEALED NO SIGNIFICANT ABNORMALITIES. I BELIEVE THIS NEAR POSSIBLE RWY INCURSION COULD HAVE BEEN PREVENTED BY PROVIDING MORE ADEQUATE SPACING BTWN LNDG ACFT. SANFORD TWR DOES AN OUTSTANDING JOB; BUT THEY MUST REALIZE THE SPACING THEY PROVIDE MAY BE ADEQUATE ASSUMING ALL GOES AS PLANNED; BUT IF NOT; PLEASE DO NOT BE SCOLDING THE PLANE ON THE RWY TO GET OFF. WE KNOW THAT AND WERE TRYING OUR BEST TO MAKE A R-HAND TURN WITH A FLAT L TIRE. WE IN THE PLANE SHOULD HAVE INFORMED TWR SOONER; BUT OUR MAIN CONCERN WAS ACFT CTL. SUPPLEMENTAL INFO FROM ACN 420196: WE HAD COMPLETED 3 TOUCH-AND-GOES IN THE PATTERN FOR RWY 9L AT SANFORD. ON DOWNWIND; TWR ADVISED WE HAD A C172 ON A 1 1/2 MI FINAL FOR A LNDG; AND CLRED US FOR TOUCH-AND-GO BEHIND HIM. I RPTED HIM IN SIGHT AND OBSERVED ANOTHER C172 XING THE THRESHOLD FOR LNDG. THE C172 THAT WE WERE FOLLOWING WAS NOT DSNDING AND APPEARED TO CROSS THE THRESHOLD AT BTWN 440-640 FT ON A LOW APCH AT THE COMPLETION OF EITHER A LOC OR NDB APCH. SINCE THE C172 XING THE THRESHOLD WAS HIGH; I ASSUMED HE WAS A LOW APCH AND THAT THE C172 THAT HAD JUST LANDED WAS THE ACFT WE WERE CLRED BEHIND. WE TURNED BASE TO FINAL AND I VERIFIED THE C172 THAT HAD LANDED WAS OFF THE RWY AND ON TXWY L. I CONTINUED THE LNDG AND AS I CLEANED UP FOR THE TOUCH-AND-GO I OBSERVED A C172 3000 FT OR SO AHEAD OF ME ON THE RWY. I BROUGHT MY ACFT TO A HALT AS TWR CALLED THE C172 DEMANDING HE EXIT THE RWY. TWR ASKED ME TO HOLD MY POS AND THANKED ME FOR STOPPING. THE C172 EXPLAINED HE WAS HAVING DIFFICULTY WITH HIS L MAIN TIRE. WHEN THE ACFT CLRED THE RWY WE WERE CLRED FOR TKOF. I LATER LEARNED THE C172 WAS FLYING AN APCH TO MINIMUMS AND THE INSTRUCTOR DID NOT ALLOW THE STUDENT CFII LOOK UP UNTIL TIME HAD EXPIRED. THEN HE TOLD HIS STUDENT TO LAND; RESULTING IN A LONG LNDG AND SUBSEQUENT BLOWN TIRE. I BELIEVE THAT BOTH OF US TOUCHED DOWN AT THE SAME TIME OR CLOSE TOGETHER AND BECAUSE I WAS FOCUSED ON MY IMMEDIATE LNDG AREA WITH NOSE DOWN THEN TRANSITION TO FLARE; THE C172 WAS OUT OF MY NORMAL FIELD OF VIEW.